Our data suggests that nerve growth factor, by enhancing the growth and development of cardiac sympathetic nerves and consequently elevating myocardial catecholamine content, results in the genesis of hypertrophic cardiomyopathy. It is anticipated that continuing studies will substantiate the similarity between NGF induced cardiomypathy and idiopathic hypertrophic cardiomyopathies in man. In addition to continuing our hemodynamic and pathological studies we are developing a radioimunoassay for human nerve growth factor so that accurate serum determinations of NGF activity can be measured in patients and families with IHSS. This assay has now become possible since in the past year we have been able to isolate human nerve growth factor from human placenta. Development of this assay and survey of families with a history of IHSS may permit us to make the link between elevated levels of nerve growth factor activity and development of hypertrophic myopathies.